A BASIC STUDY ON THE DEVELOPEMENT OF NEW TECHNIQUE FOR SELECTIVE DORSAL ROOT BLOCKADE USING SPINAL ENDOSCOPY

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1. Development of fiberoptic spinal endoscopy : We developed small diameter endoscopes for diagnostic and therapeutic use in the spinal space, and we intended to see if we can perform selective posterior root blockade using this endoscope. We made two types of endoscope, outer diameter 1.8 mm and 2.8 mm. The latter had a larger flush lumen through which a wire-type bipolar electrode for recording spinal evoked potentials can be passed. They consisted of the image fiber, light guide, a flush lumen. After small laminectomy, we inserted these endoscope carefully into epidural and subarachnoidal space. We could easily find and clearly observe structures of the epidural and subarachnoidal space, such as spinal cord, nerve roots and blood vessels.2. Development of a new technique using spinal endoscopy to identify the dorsal root as an afferent nerve from an objective area on the dermatome. : We performed a experimental study to determine endoscopically the dorsal root which correspond to th … More e specific intercostal nerve area using spinal cord evoked potential recording. After the observation of the epidural and subarachnoidal space with a endoscope, we inserted a wire type recording electrodes into the space through the lumen of endoscope or in parallel with it, and determined the location of electrodes and dorsal root. We located stimulation electrodes on lower thoracic intercostal nerves near the level of the objective root. We tried to record spinal cord potentials or dorsal root potentials generated by impulses from intercostal nerves. We obtained a series of potentials as changing the level of recording electrode from upward to downward region near the objective root. At the last of the experiment, we determined the anatomical location of the objective root and intercostal nerves. We could record evoked potentials very near to the dorsal root from both the epidural and subdural space. We found characteristic differences in shape of evoked potentials which obtained from different levels. Highest magnitude of the potential were obtained from the electrodes placed nearest to the site of entry of the dorsal root. The polarity of the spinal cord potentials changed inversely on this site. Thus we can identify the objective root using endoscopic technique coordinating with electro-physiological technique. Less